This invention relates to a process for providing the surface of electrically conductive three-dimensional substrates with a protective and decorative laminar structure and to the resultant laminar structures.
Modern automotive original lacquer coatings usually consist of a base coat/clear topcoat lacquer coating, which is applied onto a body which has been electrophoretically primed and coated with surfacer. In such coatings, the surfacer, base coat lacquer and clear lacquer are applied by spraying. Large quantities of problematic lacquer sludge are formed during the spray application in the lacquer coating process. The lacquer coating process demands elaborate logistics on the part of the vehicle manufacturer due not only to the multiple lacquer layers of different lacquer materials to be applied but also to the numerous shades in which some of the lacquer layers are produced. The base lacquer layers are thus applied in various different shades, as are the surfacer layers too by many automotive manufacturers.
In the Federal Republic of Germany, for example, vehicles marked as taxis are of a prescribed shade. Vehicles which have been used as taxis are difficult to sell as they can be recognised as former taxis. For this reason, conventional cars not painted in the taxi shade have been provided with a bonded plastic film of the taxi shade which hides the actual shade of the multi-layer lacquer coating. This film may subsequently be removed once the taxi has completed its service, so revealing the actual lacquer coating again.
The object of the invention is to provide a logistically straightforward process which avoids lacquer waste and permits the surface of three-dimensional substrates, in particular motor vehicles, to be provided with a protective coating and decorative finish. In particular, it should be possible to perform the process in an environmentally friendly and efficient manner.
It has been found that this object may be achieved by a process for the production of a three-dimensional substrate provided with a protective and decorative laminar structure, which process is characterised in that a primer layer of a coating composition (I) which is electrically conductive in the stoved state is applied without spraying onto an electrically conductive substrate and stoved, whereupon a substrate not yet in the desired three-dimensional shape is shaped, whereupon a second coating layer of an electrophoretically depositable coating composition (II) is electrophoretically deposited and stoved and whereupon a plastic film is applied.
In the process according to the invention, the conductive primer layer is in particular applied by brushing, roller application, dipping or flow coating. The conductive primer layer is particularly preferably applied using the coil coating process, by autophoretic deposition or electrophoretic deposition. The conductive primer layer may be applied onto the entire surface, i.e. both sides, of the substrate. The substrate may be in the desired three-dimensional shape even before application of the primer layer. It is also possible not to shape the substrate three-dimensionally until the conductive primer layer has been applied and stoved, wherein it has optionally previously been stamped or cut. Shaping may be achieved by the usual processes familiar to the person skilled in the art for the particular substrate, for example by deep drawing. The substrate may also be in the form of individual components which may be combined into an assembly before application of the second coating layer, wherein the individual components may already have been provided with the primer layer.
Various coating compositions (I) may be used to apply the coating layer which is electrically conductive in the stoved state, wherein no spray application methods are used according to the invention.
A first preferred embodiment of the present invention comprises a process for the production of a protective and decorative laminar structure on a three-dimensional, electrically conductive substrate, in which a primer layer of a primer coating composition (Ia) which is electrically conductive in the stoved state is applied onto both sides of a sheet metal coil using the coil coating process and stoved, sheet metal components are subsequently stamped out from the coil and shaped by deep drawing and optionally joined together into an assembly, whereupon a second coating layer of an electrophoretically depositable coating composition (II) is electrophoretically deposited and stoved and whereupon a plastic film is subsequently applied.
A second preferred embodiment of the present invention comprises a process for the production of a protective and decorative laminar structure on a three-dimensional, electrically conductive substrate having an autophoretically coatable surface, in which a primer layer of an electrophoretically depositable coating composition (Ib) which is electrically conductive in the stoved state is autophoretically deposited and stoved, whereupon a further coating layer of an electrophoretically depositable coating composition (II) is electrophoretically deposited and stoved and whereupon a plastic film is subsequently applied.
A third and particularly preferred embodiment of the present invention comprises a process for the production of a protective and decorative laminar structure on a three-dimensional, electrically conductive substrate, in which a primer layer of an electrophoretically depositable coating composition (Ic) which is electrically conductive in the stoved state is electrophoretically deposited and stoved, whereupon a further coating layer of an electrophoretically depositable coating composition (II) other than (Ic) is electrophoretically deposited and stoved and whereupon a plastic film is subsequently applied.